Digital hearing aids have been developed in recent years. For example, in hearing aids for “In-The-Ear” (ITE) and “Behind-The-Ear” (BTE) applications, an incoming audio signal is processed according to processing scheme and subsequently transmitted to the user of the hearing aid through a hearing aid loud speaker (i.e., hearing aid receiver). The processing scheme, which is used to process the incoming audio signal and to produce the processed, outgoing signal, represents the nucleus of the signal improvement which the hearing aid user experiences. This improvement may be increased speech intelligibility. Thus, the processing scheme represents methods and core knowledge proprietary to the individual hearing aid manufacturer who has developed the methods and knowledge for the application. These methods and knowledge are often referred to as algorithms.
An algorithm can be considered as a sequence of actions that need to be carried out to fulfill a task. In the case of digital hearing aids, an algorithm is a sequence of instructions that manipulate the incoming signal in addition to other processing, such as control, in order to produce an outgoing signal that generally represents an enhancement of the incoming signal. This enhancement is beneficial for the hearing impaired person who wears the hearing aid.
The digital hearing aid contains a programmable processing module called a hybrid. The hybrid is an encapsulated entity that includes integrated circuits, a circuit that connects the integrated circuits, and passive components.
The hearing aid has a connector through which the hearing aid is connected to an external fitting device. The external fitting device is connected to a PC (Personal Computer) or similar device in which fitting data is generated. The hearing aid connector is connected internally in the hearing aid to the access port of the hybrid. Data is downloaded from the PC to the integrated circuits in the hybrid through the access port.
The hybrid serves as the basis for multiple hearing aids developed by different manufacturers. In other words, one hybrid can execute a multitude of algorithms due to the flexibility and programmability that comes with an open platform type of processing system. Open platform in this context means the ability to develop and execute a multitide of algorithms as described above. For example, two competing hearing aid manufacturers, who use the same type of hybrid originating from a common vendor, can execute two or more completely different algorithms in the hearing aids. Currently available open hybrid(s) do not prevent access to the embedded application code from an external device. Thus, it is possible to gain unauthorized access to application code in a hybrid, for purposes of reverse engineering or to deploy the code in another hybrid.
There is a need to provide a method and system for protecting any critical content stored in a programmable system.